A while ago I've written a patch to qjackctl which adds DBUS support to start and stop the JACK audio server. It's available and enabled by default in qjackctl from version 0.3.4.11 upwards.

The main use-case for it is to bring up the JACK server after a suspend/resume cycle on laptops. More information about this is available on a Wiki Page. This blog will just give minimal usage information to tease you :)

An example script to re-launch JACK with the last chosen preset looks like this: